In plantations currently increasing by 1,700 acres a year in the Southern Highlands Province of Tanganyika, a number of diseases have recently become important in the present total of 5,000 acres of pine. Die-back induced by boron deficiency is the most important and is the subject of a comprehensive research programme which has so far shown that the condition can be alleviated but not cured by a ground dressing or foliar spray containing borax. Severe yellowing in the biggest planting scheme may be caused by a major nutrient deficiency, but experimental evidence is not yet available. Dead top similar to that reported from Kenya has been recorded but it and other presumed deficiency diseases are of secondary importance.PestalotiopsisandDiplodiafungi have been found associated with heavy needle-cast and may be its primary cause.Armillariais at present of secondary importance. Lepidoptera and thrips have damaged pines in several areas. The biggest volume-producer,P. radiala, is by far the most severely affected by disease, but other pines (e.g.P. palula, higher and moister sites;P. elliottii, lower and drier) have so far been relatively free from disease.